List of free playground tool/service for developerππ½

Flatbase
Query your CSV and JSON files with SQL. Flatbase is the data science platform for developers. Upload files, write SQL, visualize results, and share with collaborators.
Tag: sql, json, api, playground
Up to 3 workspaces Share with up to 3 teammates

csplayground.io
Bring self-paced interactive coding courses to classrooms. Build your own lessons and monitor students' progress.
Tag: playground, education
All courses Create custom course Classroom management Student progress tracking 5 students

Unlimited public Pens and Collections Unlimited templates Debug view (requires log in) 1 project with 10 files

Codesandbox
Where teams build faster, together. Create, share, and get feedback with collaborative sandboxes for rapid web development.
Tag: IDE, playground
Free for individuals β All Platform features β Public sandboxes β Personal workspace

Trinket
Share Code from any Device. Trinket lets you run and write code in any browser, on any device.
Tag: course-builder, teaching, playground, web-development
Unlimited Basic Trinkets Python, HTML, GlowScript, Blocks and more Quick, Simple Sharing Remixing Customizable Code Editor Downloadable Code Free Activities Custom Courses

Projects and code are public by default Full-stack apps that sleep after 5 minutes Unlimited static sites that are always on Github import/export and Prettier support

SQL Online IDE
User-friendly interface for data science. No registration for start, No DownLoad, No Install. Online test SQL script.
Tag: sqlite, mysql, database-gui, playground